This paper addresses the unfairness problems of a DQDB network through a structured access remedial scheme, namely the Dynamic Three-Tier protocol. At low load domains, it retains the original 802.6 (no Bandwidth Balancing Mechanism, (BWB) protocol performance. At heavy loads, it activates a dynamic bandwidth control mechanism, called the Alpha Tuning Mechanism. With the right choice of the α parameter, the match of the service pattern (rendered by the proposed protocol) and the actual demand (or traffic) pattern in the network is achieved. Between these domains, at normal loads, it uses an anticipatory demand function (Δ) to address latency-related unfairness. The proposed protocol's performance is investigated over different load types and load values, with single- and multiple-packet-sized messages. In each scenario, the proposed protocol is capable of delivering better performance over the current 802.6 (with BWB) standard. Its effectiveness and dynamic capabilities are very impressive.

The alpha tuning mechanism for distributed queue dual bus (DQDB) networks is proposed. This mechanism achieves a match between the users' demand and the resulting protocol's service patterns. The use of a tunable /spl alpha/-parameter (representing some fictitious user population) and access protection lead to a dynamic bandwidth control capability. The inherently position dependent fairness problems of DQDB are overcome, especially at heavy loads. Fairly uniform delays and uniform success rates of transmission are seen for every user. Analysis and simulation studies for different load patterns, show that it outperforms the bandwidth balancing mechanism (BBM). This mechanism may be extended to any unidirectional channel, to achieve demand and service pattern match.

This paper addresses the unfairness problems of a DQDB network through an structured access remedial scheme, viz., the dynamic 3-tier protocol. At low load domains, the original DQDB protocol performance is retained. At heavy loads, a dynamic bandwidth control mechanism, named Alpha Tuning Mechanism, is activated. With the right choice of the /spl alpha/-parameter, it is possible to match the service pattern (in terms of channel bandwidth) offered by the access protocol with the actual demand (or traffic) pattern in the network. At low load domains an anticipatory demand function (/spl Delta/) addresses latency related unfairness. The results demonstrate the effectiveness of this approach.>

Iterative flow control algorithms to achieve a Pareto optimal point have been proposed in the telecommunications literature. In this paper, we present several relaxation and estimation techniques to improve the performance of the algorithms. We also explore several possible implementations that extend support to the proposed analytical models. Simulations of these possible implementations are carried out, and the performance of the flow control algorithms studied. The proposed implementations for the Pareto algorithms achieve optimization of the product of powers of individual user classes. The effect of additional factors like the length of the observation cycle, the structure of the observation cycle, and the relaxation factors are also studied. The simulation results suggest that better convergence is achieved when the observation windows are maintained at the node level and are packet count based. The window size has to be sufficiently long. The relaxation techniques are useful with the right choice of relaxation factors. The greedy algorithms using estimation techniques to achieve complete decentralizability are very appealing.

The authors discuss the unfairness issue arising in a 802.6 distributed queue dual bus (DQDB) network at heavy loads. Based on the 802.6 protocol, the end-nodes along a bus experience longer delays than the other nodes. The origin and remedy for this heavy load unfairness problem are discussed. An access control scheme is proposed as a solution. A comparison of the proposed scheme with the 802.6 protocol is presented. The simulation results and performance characteristics are discussed under several types of loads. With symmetric load conditions under the proposed scheme, all active nodes along a bus experience almost the same access delay and packet loss characteristics. The performance under several other load conditions was also found to be satisfactory.>